Absorption of Radon through the Skin and Its Exhalation through the Lungs

There are numerous reports in the medical literature that the local application of ointments containing radon have therapeutic effects on deep-lying structures, such as joints, muscles, and blood vessels (1, 2, 3, 4). On the other hand, there is the well established physical fact that the alpha rays from radon and from its short-lived decay products, radium A and radium C1, have a range, or penetration, of not more than 30 to 50 microns in tissue. Because one of us (5) had observed lasting and deeply penetrating effects on the vascular structures of an area treated with ointments containing radon, it appeared interesting to follow the fate of the radon (a chemically inert gas) originally contained in the ointment, to determine to what extent it enters the tissues. If it could be shown that radon does enter the tissues, deep effects of radon ointment therapy would be understandable. Once present in the blood stream, this absorbed radon should be transported to the lungs, and a portion of it should then be exhaled in the expired air. Measurements of the radon concentration in samples of expired air, together with knowledge of the expiration rate, permit a direct evaluation of the minimum quantity of radon absorbed from ointment, and hence available for the alpha radiation of tissues at a distance of more than 50 microns from the site of application.4 The breath sampling and radon measurements were made by standard technics (6). The experiments were carried out on normal intact skin, as well as on the surface of large post-phlebitic leg ulcers, which, however, were very poorly vascularized as demonstrated by repeated fluorescein tests (7). The ointment in every instance contained 44.4 microcuries of radon per c.c. (49 microcuries per gm.) of lanolin. The thickness of the application varied between 2 and 3 mm. The areas were immediately covered with oil silk or a watchglass and then sealed with several layers of adhesive. In the first group of experiments, samples of the exhaled air were taken after 20 minutes, 2⅔ hours, and 4½ hours. At each sampling time a specimen of the room air was taken and analyzed for its content of radon. In the first experiment, on three patients, possible inhalation of radon from the ointment during the procedure of application was largely inhibited by having the windows of the large ward wide open and creating a draft away from the patient's mouth toward the foot end of the bed. Table I indicates that approximately 2.4 per cent of the radon applied was exhaled within the first 4½ hours when the ointment was applied to the leg ulcer, while the amounts absorbed under the same circumstances from normal skin and exhaled were only 0.13 per cent and 0.08 per cent for the same period. In the second experiment further precautions were taken to prevent inhalation of radon during the application of the dressings. During this period the patient breathed oxygen from a B.M.R. machine.